Chapter 5: HIV Tests Flashcards
What was the first HIV diagnostic test based on
Was based on the ELISA (enzyme linked immunosorbent assay) principle but lacked sensitivity until it underwent many advances.
What is sensitivity and specificity of HIV tests
Sensitivity of tests is the ability to pick up very low levels of antibodies.
Specificity of tests is it’s ability to disregard the presence of antibodies that are not specific to HIV.
Why is it important to test for HIV
To screen donated blood
Research transmission patterns and prevalence of virus
Diagnose HIV in people
Monitor progress of infection
Monitor response to antiretroviral therapy
Detect drug failure
Previously it was to diagnose or confirm suspected HIV infection in people who experience certain symptoms or diseases.
Explore the 2 diagnostic approaches to diagnosing HIV
Identification of the virus.
Some detect p24 viral antigen in blood and others can detect viral nucleic acid in blood.
Detection of an immune response to HIV
Production of antibodies and cellular response Inc specific CD4+T cell responses.
Discuss HIV antibody test
Usually done on blood with 4 major components and can also be detected in saliva and urine.
Well-known antibody tests include Rapid HIV antibody test
ELISA
Western blot test
These tests can’t trace virus in blood but react to HIV antibodies that are formed when immune system attempts to protect body against virus. The test becomes positive after host has mounted an immune response and serconverted.
What is the window period
Is the period between HIV infection and the appearance of antibodies that can be detected by antibody test.
What are the advantages of rapid HIV tests
Easy to use
Less invasive
Inexpensive
Easily transportable
What are the advantages of saliva rapid tests
Is very easy to use
Not intrusive as blood test
Painless
Avoids hazard of person sustaining a needle stick injury
Can be used where it’s difficult to take blood like with children and drug users
Diagnosis of HIV infections with viral tests are based on what ?
Detection of viral antigens like p24
Detection of viral nucleic acid
Isolation of virus in lymphocyte cell culture
P24 antigen and HIV PCR techniques are some well-known HIV viral tests because they detect HIV particles in the blood and yield a positive result much sooner.
Discuss the p24 antigen test
Detects predominant HIV antigen in blood. It is the main protein of the core of the virus and can usually be detected in blood shortly after infection.
DBS test is useful because
Inexpensive
Easy to use
Not very invasive
Not very hazardous
What test is used for proviral DNA detection
HIV DNA PCR technique which is used to
Diagnose babies younger than 18 months
Excludes existing HIV infection
Screen donated blood
Test HIV vaccine recipient
What test is used for viral RNA detection
RNA PCR used in early detection of HIV infections. Mainly used for
Measure response to antiretroviral therapy
Monitor progress
Test new therapy
Detect drug failure
Discuss the HIV counseling for adolescents and adults
Group info session offered to clients to outline benefits of HCT
Group sessions followed by individual sessions to answer any additional questions and clarify misunderstanding
After consent has been given a rapid HIV tests should be carried out
If 1st test is negative client consider to be HIV uninfected and receive post test counseling
If 1st rapid HIV test is positive a confirmatory test must be performed with a different rapid test. If both tests are positive person considered HIV positive.
Discuss the HIV counseling for children younger than 18 months
Check every child at Every health care visit.
If mom is positive baby should be tested with HIV PCR test at birth.
If baby tests positive with HIV PCR then a second test must be done and ART started immediately.
Discuss the HIV counseling for children 18 months and older
Every Child check at every health care visit
If mom is positive then child must be screened with rapid HIV tests
If child positive then confirmatory test must be done
All HIV positive children must start ART.
